Particular blood cells (macrophages, granulocytes, neutrophils, polymorphonucleated) respond to a chemical stimulus (when stimulated by substances called chemokines) by migrating along the concentration gradient of the stimulating agent, through a process called chemotaxis. The main known stimulating agents or chemokines are represented by the breakdown products of complement C5a, some N-formyl peptides generated from lysis of the bacterial surface or peptides of synthetic origin, such as formyl-methionyl-leucyl-phenylalanine (f-MLP) and mainly by a variety of cytokines, including Interleukin-8 (IL-8, also referred to as CXCL8). Interleukin-8 is an endogenous chemotactic factor produced by most nucleated cells such as fibroblasts and macrophages.
In some pathological conditions, marked by exacerbated recruitment of neutrophils, a more severe tissue damage at the site is associated with the infiltration of neutrophilic cells. Recently, the role of neutrophilic activation in the determination of damage associated with post ischemia reperfusion and pulmonary hyperoxia was widely demonstrated.
The biological activity of IL-8 is mediated by the interaction of the interleukin with CXCR1 and CXCR2 membrane receptors which belong to the family of seven transmembrane receptors, expressed on the surface of human neutrophils and of certain types of T-cells (L. Xu et al., J. Leukocyte Biol., 57, 335, 1995). Selective ligand are known which can distinguish between CXCR1 and CXCR2: GRO-α is an example of a CXCR2 selective chemotactic factor.
Potential pathogenic role of IL-8 in pulmonary diseases (lung injury, acute respiratory distress syndrome, asthma, chronic lung inflammation, and cystic fibrosis) and, specifically, in the pathogenesis of COPD (chronic obstructive pulmonary disease) through the CXCR2 receptor pathway has been widely described (D. W P Hay and H. M. Sarau., Current Opinion in Pharmacology 2001, 1:242-247).
Characteristic neutrophil accumulation occurs in acute and chronic pathologic conditions, for example in the highly inflamed and therapeutically recalcitrant areas of psoriatic lesions. Neutrophils are chemotactically attracted and activated by the sinergistic action of chemokines, IL-8 and Gro-a released by the stimulated keratinocytes, as well as of the C5a/C5a-desArg fraction produced via the alternative complement pathway activation (T. Terui et al., Exp. Dermatol., 9, 1, 2000).
Novel classes of potent and selective inhibitors of IL-8 biological activities (R-2-arylpropionic acid amides and N-acylsulfonamides) have been described as effective inhibitors of IL-8 induced neutrophils chemotaxis and degranulation (WO 01/58852; WO 00/24710). Furthermore, novel subclasses of R and S 2-phenylpropionic acids have been described (WO 03/043625) as potent IL-8 inhibitors completely lacking the undesired cyclo-oxygenase enzyme (COX) inhibitory effect. The inhibition of prostaglandin synthesis deriving from COX inhibition involves, in fact, an increase of cytokine production which results in the amplification of the undesired pro-inflammatory effects of neutrophils.